Java Interview Questions » Uncategorized

File Uploading Using Servlet

Ramakrishna — Mon, 26 Jan 2009 15:30:33 +0000

FileUploading Using Servlet(JAVA)

This is an example of the file Uploading in Java using Servlets . This file uploading concept Works with the Java as follows

The Servlet api consists of the method called getContentType which takes the file request as the input and generates the file to the specified path

Here is the Code of the file Uploading using Servlets in JAVA

Name the HTML page as file.html

Specify the action path to which servlet to must follow and the type of the data to send to the servlet is specified by the enctype=”multipart/form-data”

Once the request goes to the servlet the request is collected through getContentType() method (to learn more about getContentType)

Write the servlet code and specify the name of the servlet as UploadFile.java

package com.myapp.struts;

import java.io.*;
import java.sql.*;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.ServletInputStream.*;
import java.io.PrintWriter;

public class UploadFile extends HttpServlet {

public void doPost(HttpServletRequest req,HttpServletResponse res)
{

try{

//out.println(“
Content type is :: ” +contentType);
//to get the content type information from JSP Request Header

String contentType = req.getContentType();
int flag=0;
FileInputStream fis=null;
FileOutputStream fileOut=null;

//here we are checking the content type is not equal to Null and as well as the passed data from mulitpart/form-data is greater than or equal to 0

if ((contentType != null) && (contentType.indexOf(“multipart/form-data”) >= 0))
{
DataInputStream in = new DataInputStream(req.getInputStream());

//we are taking the length of Content type data

int formDataLength = req.getContentLength();
byte dataBytes[] = new byte[formDataLength];
int byteRead = 0;
int totalBytesRead = 0;

//this loop converting the uploaded file into byte code

while (totalBytesRead < formDataLength) {
byteRead = in.read(dataBytes, totalBytesRead,formDataLength);
totalBytesRead += byteRead;
}

String file = new String(dataBytes);

//for saving the file name

String saveFile = file.substring(file.indexOf(“filename=\”") + 10);
saveFile = saveFile.substring(0, saveFile.indexOf(“\n”));
out.println(“savefiledddd “+saveFile);
int extension_save=saveFile.lastIndexOf(“\”");

//Here we are invoking the absolute path out of the encrypted data

saveFile = saveFile.substring(saveFile.lastIndexOf(“\\”)+ 1,saveFile.indexOf(“\”"));
int lastIndex = contentType.lastIndexOf(“=”);
String boundary = contentType.substring(lastIndex + 1,contentType.length());
int pos;

//extracting the index of file

pos = file.indexOf(“filename=\”");
pos = file.indexOf(“\n”, pos) + 1;
pos = file.indexOf(“\n”, pos) + 1;
pos = file.indexOf(“\n”, pos) + 1;
int boundaryLocation = file.indexOf(boundary, pos) – 4;
int startPos = ((file.substring(0, pos)).getBytes()).length;
int endPos = ((file.substring(0, boundaryLocation)).getBytes()).length;

out.println(“savefile”+saveFile);

String pathname_dir=”D:\\test\\”+saveFile;
File filepath=new File(pathname_dir);
out.println(“filepath_ “+filepath);
fileOut = new FileOutputStream(filepath);
fileOut.write(dataBytes, startPos, (endPos – startPos));
fileOut.flush();
fileOut.close();
fis.close();

}

}catch(Exception e)
{
System.out.println(“Exception Due to”+e);
e.printStackTrace();
}
}
}

Here you are specifying the path that the file is to save in your local disk i.e

your file will be saving in the test foldar with the name of the file as orginal name of the file you are invoking.

Here is Deployment discriptor to pass the request from the html to Servlet program. save these with the name web.xml in the WEB-INF directory

UploadFile
com.myapp.struts.UploadFile

UploadFile
/servlet/UploadFile

Note: If You want the code in the jsp follow the link JSP File Uploading

Random Posts

Explain Interface?Define

Ramakrishna — Tue, 16 Dec 2008 18:03:18 +0000

Interface:

In Java language, an interface is like a stripped-down class; it specifies a set of methods that an instance must handle, but it omits inheritance relations and method implementations.

Object-oriented programming is sometimes modeled as communication between objects like one object talks to, or sends a message to, another object ( by invoking a method on it ). An object needs to know the order to talk with another object ; a set of abstract methods i.e., method minus implementation information. Put the another way, an interface specifies how we can talk to an object,but says nothing about what kind of object will handle our messages. It is job of one or more class instances to provide the substance behind an interface’s promise.

The general form of an interface definition is :

interface name

{

variable declarations;

method declarations;

}

Here, interface is the keyword and name is any valid Java variable ( just like class names ).

Variables are declared as follows:

public static final type variableName = value;

Methods declaration will contain only a list of methods without any body statements.

Example:

return-type methodName(parameter_list);

The following is an example of an interface definition that contains two variables and one method :

interface Item

{

public static final int prodCode = 1001;

public static final String prodName = “Fan”;

public abstract void display();

}

Here the code for the method is not included in the interface and the method declaration simply ends with a semicolon. The class that implements this interface must define the code for the method.

NOTE:

–> All the Interface methods are Abstract only by Default.

–> we can’t create an object to the interface. But we can create a reference variable to interface.

–> Once the interface is provided we can create ‘n’ number of implementation classes

–> we can create object to implementation class by using this we can allow all features of the super class.

Random Posts

URL Connection Class

Ramakrishna — Fri, 12 Dec 2008 17:58:37 +0000

URL Connection Class

The URLConnection class provides a more granular interface to a URL than the getContent method in the URL class. This class provides method for examining HTTP headers, getting information about the URL’s content, and getting input and output stream to the URL.

Some of the methods used in these URL Connection Class are as follows

public abstract class java.net.URLConnection extends java.lang.Object {
protected java.net.URL url;
protected boolean doInput;
protected boolean doOutput;
protected boolean allowUserInteraction;
protected boolean useCaches;
protected long ifModifiedSinces;
protected boolean connected;
static java.net.ContentHandlerFactory factory;
public static synchronized java.net.FileNameMap getFileNameMap();
public static void setFileNameMap(java.net.FileNameMap);
public abstract void connect() throws java.io.IOException;
protected java.net.URLConnection(java.net.URL);
public java.net.URL getURL();
public int getContentLength();
public java.lang.String getContentType();
public java.lang.String getContentEncoding();
public long getExpiration();
public long getDate();
public long getLastModified();
public java.lang.String getHeaderField(java.lang.String);
public java.util.Map getHeaderFields();
public int getHeaderFiledInt(java.lang.String,int);
public long getHeaderFieldDate(java.lang.String,long);
public java.lang.String getHeaaderFieldKey(int);

Random Posts

Collection FrameWork

Ramakrishna — Thu, 06 Nov 2008 01:40:24 +0000

Q) What is Collection FrameWork?

Res) A Collection FrameWork represents a class library to handle groups of objects

–> Collection framework is implemented in Java.Util.Package.

–> Collection does’t store copy of all the object, but it stores references of all objects.

–> Collection classes will act upon only referenced datatypes they do not act upon primitive datatypes.

Random Posts

Difference between session.save() and session.saveOrUpdate()

Ramakrishna — Tue, 02 Sep 2008 17:34:30 +0000

Q) Difference between session.save() and session.saveOrUpdate()?
A)
session.save() – Insert data into the table
session.saveOrUpdate()- Insert data if primary key not exist otherwise update